How can I create this color rock?

Pick up a copy of this book.

http://www.sceneryexpress.com/...fo.asp?number=WD1207

You're going to want to base-coat the surface and then dry brush the highlights.

For a base coat, I use a flat latex paint from Lowe's, the color is called Volcanic Ash. Pull the gray paint card, I'm sure you'll find a color to suit. Base-coat and let dry.

Step two. The wash. I'd try a little black acrylic latex paint (comes in tubes from the craft store) in a spray bottle and dilute with warm water. Just squirt it on and let it run into the cracks. Wait and let this dry.

Then to dry brush. Basically you're going to put a dab of acrylic latex paint on a scrap of cardboard and slap your brush around in it. Then brush most of it off (like you do when you finish cleaning your brush) and then go over your "rock" like you're dusting the furnature. I'd suggest antique white for the lighter and maybe a green mixed with a little of the Volcanic Ash for the mossy parts.

Have fun, it's easy. Worst case if you don't like it just repaint with your base color and start over.

Gilly

Get a sledgehammer...and you'll instantly have many of them with that EXACT color!!

Use Rich Battista's methods from his videos...and experiment with color variations.

Rick

Craft store acrylic white and black mixed to a color a few shades darker than you want for the final color. Then dry brush with the antique white as Gilly describes.

Jim

Beautiful work Jim...just beautiful.  Is that all you used was the stone mix of the two craft paints and then dry brush with antique white?  Any others?  Any black wash at any point and if so when and what mixture?

Thanks, John.

I used just the black and white craft paint and then the drybrushing. When applying the initial gray color I dipped the brush in water occasionally to help the paint flow into the crevices. The deep texture of the rock castings provided plenty of shadows by themselves.

A black wash could be added after the gray is totally dry if you want more contrast. About a mix of 1 part black paint to 2 parts water would work.

Be sure everything is totally dry before adding the wash and before attempting the drybrushing. When drybrushing, the less paint on the brush the better. You just want to add some lighter color to the edges of the rocks.

It's really not too hard. Just keep practicing, and if you don't like the result go back and paint it again as Gilly said. A coat of flat white latex will bring you right back to square one if necessary.

This was a small area of rock, but if I have a lot of rock to color, I sometimes use regular flat interior latex paint for the white and black...or you could have them mix up a medium gray for you.

Jim

These much smaller rocks (from Plaster of Paris) were colored using an I/A wash, no base coat, no drybrushing.  Once the wash is added I just burnished them with a rag or napkin, or perhaps my fingers (Since they are always within reach).

Just like they said above.  We used some oops paint from HD for the base.  This is done on layers of pink foam board, not plaster but the same results.  A lot of this was done by a 8 y/o son, with a little guidance.  Jim had a Thanksgiving issue that described how to do this, not sure on the run #.  One tip, make sure your base coat covers every little crack or it will stick out like a sore thumb when dryed.  Nick  

Go to the store and buy some colors that you like.  Craft paint is pretty cheap.  Try them and then add white or black if not quite right.

Oh, and --- Vulcan

What is an I/A wash?

I assume it's a very cool way to refer to isopropyl alcohol, although I don't know what the backslash is about.

Ink/Alcohol. 

Sorry, I thought everybody knew what I/A was. It's isopropyl alcohol with india ink. Rule of thumb has it mixed 1 teaspoon ink to 1 pint alcohol. I mix several different degrees of black. Light-medium-dark.